It has previously been proposed to form shingles from asphalt squares wherein the shingle is provided with a pair of slots adjacent one corner which permits corner portions of a shingle from an upper course of shingles to engage beneath edge portions of an adjacent pair of shingles of a lower course, so mechanically locking that corner portion of the upper shingle to the lower shingles. However, due to the resiliency of asphalt shingles, the mechanical interlock is insufficient to provide a good weather seal between shingles. Moreover, the slotting of asphalt shingles adjacent to areas that are relatively highly stressed can lead to premature failure of the shingle.
Metal roofing shingles are well known in the art. Many of the prior proposals relate to providing mechanical interlocks between adjacent shingles layed on the same course and/or between shingles of adjacent courses, which interlocks are formed by relatively tightly overturning margins of the shingles along their length, to form channels having a hooked cross section, mid hooking the margins of adjacent shingles together. It is found that capillary action can lead to leakage.
One of the disadvantages of metal shingles arises from their high thermal conductivity. Although in many of the prior art proposals the overturned margins of the shingles provided for interlocking purposes will serve to raise the central areas of the shingle from the underlaying roof structure and to create a small air space, this is generally insufficient for insulating proposes. It is also insufficient to permit heating cables or the like to be located under the shingles.
Another disadvantage of metal shingles of the raised type is that central areas thereof are not well supported whereby they tend to be permanently deformed under only moderately heavy loads.
Yet mother disadvantage, particularly in those types wherein the edges are folded under so as to be linkable with another shingle in side by side relationship is that it is difficult to conform these shingles to irregularities in the supporting roof structure.
It is an object of this invention to provide metal roofing shingles having a simple interlock provision.
It is a further object of this invention to provide such shingles which provide good mechanical sealing capability, while minimizing the possibility of leakage due to capillary action.
A still further object of this invention is to provide metal roofing shingles of increased load beating capacity.
It is yet another object of this invention to provide metal roofing shingles that minimize the metal to metal contact area between shingles while being maintained in substantially spaced apart relation from underlaying shingles and roof structure so as to provide increased insulation capability, and also to permit heating cables or the like to locate beneath the shingles.
It is yet another object of this invention to provide metal roofing shingles that are amenable to being deformed in an intentional manner while being layed so as to overcome small irregularities in the underlaying roof structure.
It is still another object of this invention to provide metal roofing shingles which provide an attractive appearance of thickness so as to give a distinctive sculptured look when the shingles are installed on a roof.